1. Field of the Invention
The present invention relates to a temperature control device of an optical semiconductor device needing an environment which is less changed in temperature, particularly to that having temperature detecting points where the optical semiconductor device is clamped at both sides, in which one is susceptible to an ambient temperature and the other is not susceptible to the ambient temperature rather than the optical semiconductor device to the ambient temperature, and wherein an average temperature at both temperature detecting points is constant, thereby controlling the temperature of the optical semiconductor device.
2. Prior Art
A conventional temperature control device of an optical semiconductor device of this type is used for permitting the temperature of optical semiconductor device, etc. to keep constant. FIG. 4 is a block diagram showing one example of a construction of the conventional temperature control device of an optical semiconductor device. In FIG. 4, a thermal conductor 2 is a block made of a material of high thermal conductivity such as copper, iron, etc. An optical semiconductor device 1 is fixed to a surface 2a of the thermal conductor 2 and a Peltier element 5 is jointed to one side surface of the thermal conductor 2 at a jointing surface 5a.
A temperature detecting circuit 6 detects the difference between a temperature of the thermal conductor 2 at a temperature detecting point 12 to which the optical semiconductor device 1 is fixed and a set temperature, and output a temperature detecting signal to a temperature control circuit 4. The temperature control circuit 4 controls a Peltier driving current for applying to the Peltier element 5 in response to the temperature detecting signal. The Peltier element 5 changes the temperature of the jointing surface 5a of the thermal conductor 2 upon a reception of the Peltier driving current, thereby controlling the temperature of the optical semiconductor device 1 by way of the thermal conductor 2.
The operation of the temperature control device of an optical semiconductor device will be now described. When the ambient temperature is changed, the temperature of the optical semiconductor device 1 and that of the thermal conductor 2 to which the optical semiconductor device 1 is fixed are also changed. The temperature detecting circuit 6 detects the difference between the temperature of the temperature detecting point 12 and the set temperature, and output a temperature detecting signal to the temperature control circuit 4. The temperature control circuit 4 controls the Peltier driving current to be applied to the Peltier element 5 so as to secure a negative feedback in response to the temperature detecting signal.
When the Peltier driving current to be applied to the Peltier element 5 is changed in its direction, the thermal conductor 2 is cooled or the temperature of the temperature detecting point 12 of the heated thermal conductor 2 becomes a set temperature. In such a manner, when the temperature of the thermal conductor 2 is detected to control the temperature of the temperature control device of an optical semiconductor device so as to permit the temperature of the thermal conductor 2 to be constant, thereby keeping the temperature of the optical semiconductor device 1 fixed to the thermal conductor 2 constant.
However the conventional temperature control device of an optical semiconductor device has a problem in that since the temperature detecting point 12 is spaced apart from the optical semiconductor device 1, and hence it is susceptible from the ambient temperature so that there occurs a difference of temperature between the temperature detecting point 12 and the optical semiconductor device 1.